Aaron Eckhart has worked with a number of standout writer-directors -- Steven Soderbergh, Jason Reitman and Christopher Nolan, to name a few -- over his 25-year film career. So when the opportunity to work with Matthew Weiner on his new star-studded Amazon anthology series, The Romanoffs, came up, Eckhart jumped at the opportunity.

Appearing in the premiere episode, “The Violet Hour,” which is now streaming, Eckhart plays Greg, the lone nephew and caretaker to a bigoted, wealthy aunt played by Marthe Keller. Over the course of the episode, which is set in Paris and is acted mostly in French, the family’s connection to the Romanovs is revealed as an unexpected person changes the course of Greg’s future.

“It was beautifully written,” Eckhart tells ET of the script. “I thought that Matthew was putting relationships together that were unconventional.”

While the actor briefly lived in France for a period of time, this was the first time he acted almost entirely in a foreign language. “I loved it,” he says of the experience, adding that he learned French while staying in the country. “I spoke French most of the time I was there, you know, to my driver, when I went out to eat and just walking around. Then I would speak to the crew.”

His ability to understand both languages certainly helped when it came to filming the episode directed by Weiner, who the actor says didn’t know the language and “speaks very quickly. So there was a bit of that lost-in-translation moment every once in a while.” Despite interpreters on set working with Eckhart’s French-speaking co-stars, Keller and Ines Melab, as well as the crew, he says there would occasionally be a “blank stare.”

But the cast and crew persevered to deliver a bitterly funny episode -- the first of eight that explores unexpected connections to the Russian dynasty. “It was very interesting watching the process and being part of it,” Eckhart says, adding: “And finally seeing it!”

The episode marks Eckhart’s brief return to the screen after 2016’s string of back-to-back releases including Sully and London Has Fallen. His next film will see him revisiting history -- the 1942 battle of Midway -- in Roland Emmerich’s Midway, co-starring Woody Harrelson, Luke Evans and Mandy Moore.

Meanwhile, one of Eckhart’s biggest hits, The Dark Knight, recently celebrated its 10th anniversary over the summer, as numerous stories reflected on the lasting legacy of the superhero film -- the second of Nolan's Batman trilogy -- in which the actor played Harvey Dent opposite Heath Ledger’s Joker and Christian Bale’s Bruce Wayne.

“I’m not surprised,” Eckhart says of the attention still surrounding the film, “because I think it is, in particular, the best of the genre. It launched the renaissance of the genre. It is all the characters in the storylines and the themes and the action that goes into it; it was unprecedented. Heath’s character set the world on fire. To this day -- I just saw a meme with the Joker face today -- it doesn’t go away. He is in the psyche of the world and I don’t know if any other characters have really done that.”

While the Joker’s story is being revisited in a new film by Todd Phillips with Joaquin Phoenix taking over the titular role, Eckhart has no intention of returning to the world of Two-Face -- either on film or as part of DC Comics’ new streaming service DC Universe, which has multiple original series in development.

“That’s something that I’ve done, and I’m too old for that,” Eckhart says, adding: “But I was very, very proud and honored to be part of that.”